This blog discusses current weather, weather prediction, climate issues, and other topics

Sunday, May 15, 2011

An Unusual Spring Rain

Our rain has even made CNN:

SUNDAY NIGHT UPDATE: Sea Tac broke its daily records for both Saturday and Sunday. A number of stations in the south Sound received 1.5-2 inches of rain today.

For days the numerical models indicated substantial rain over the weekend, and yesterday's runs really took me back. Here is the forecast 48-h rainfall totals ending 4 AM on Monday. The pinks indicate 1.28-2.56 inches stretching from normally try eastern Oregon, across the Cascades, into south/central Puget Sound territory, and then over the Olympics. Even some scattered blacks (2.5-5 inches!)

The rain started east of the Cascades on Saturday and moved into western Washington during the early evening. Here are the radar images for last night (8 PM) and Sunday morning. Serious rain!

And this rain is NOT coming from a pineapple express (moisture streaming out of the SW, starting in the tropics and subtropics), but from the southeast and is associated with a deep upper trough (see upper level map).This pattern brings clouds and precipitation to southern California as well. Snow is hitting the Sierras and even the California coastal mountains.

Even the satellite imagery shows how complex the situation is. Here you can see the band over us, but you can also see a low circulation off of northern CA.

The models are verifying well...here is the 24-h precipitation (ending roughly 7 AM Sunday) from the cooperative observed network called CoCoRahs. The south sound is getting hammered with 1-1.5 inches already.

Many stations will break their daily records today and some may reach in one day their normal monthly totals.

And don't forget eastern Washington where the Mazama-Chelan area received 1-1.5 inches. And Mark Albright, past WA State Climatologist, noted that Yakima with 1.76 inches in the past 18 hours alone is wetter than any May since 1948 when 2.76 inches of rain fell. The 2nd wettest May total was 2010 with 1.46 inches in Yakima. The total so far in 2011 is 1.90 inches through late morning 15 May 2011. Mean May precipitation in Yakima is 0.54 inches.

But want some good news? Most of the models are now indicating a major improvement towards the end of next week and next weekend....we are talking warm and getting into the 70s! Dry. Suitable for raking out the moss in your grass.

I think a great deep rain soak followed by a dry spell is fantastic for putting in my garden... I've got all my seeds and such and I can't wait! But do we risk the tomato plants, or wait (my dad's) traditional two more weeks? He always put the tomato plants out on Memorial Day weekend. What say you, Cliff? When will YOU put your tomato plants out this year?

An overnight science field trip left this morning from Nathan Hale High School, headed to the Olympic Peninsula for some experiential science activities. Clearly, one of their major experiences will involve climate!

Cliff - I traveled from Missoula to Bellevue on Saturday 5/14. From Spokane to Vantage on I-90 there was strong side wind from the north which forced me to turn right for 160 miles. The wind across the Columbia River bridge at Vantage was especially strong. The wind farm just west of the river was going full tilt. What was the reason for such strong winds?

When we came down the west side of Snoqualmie Pass there was about a 5 mile stretch of intense rain which reduced visibility to a few hundred feet. But then we quickly ran out of it and even got a few sun breaks. Why was the rain so intense in such a small area?

Don said: "With this weather coming out of the SE, why no rain shadowing on the westside?"

That's because the lift isn't orographic (mountains pushing up the airflow) but from diffluence and isentropic lift (from warm air advection dragged around the bottom of the low?) as the AFDs had been talking about for a couple of days. Even with comments that the whole office was talking about this odd system.

I'd like to hear more about how the lift is generated in this system from Cliff (if he has the time).

It's really nice that the models (particularly GFS but not the NAM) got the QPF right.

Even the vorticity in the 500mB chart is not that high where the rain band is.